A3G4250D datasheet(19/44 Pages) STMICROELECTRONICS

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A3G4250D

Main digital blocks

Doc 022768 Rev 3

19/44

Figure 9.

Stream mode

3.2.4

Retrieve data from FIFO

FIFO data is read through the OUT_X, OUT_Y, and OUT_Z registers. When the FIFO is in

stream, trigger or FIFO mode, a read operation to the OUT_X, OUT_Y or OUT_Z registers

provides the data stored in the FIFO. Each time data is read from the FIFO, the oldest pitch,

roll, and yaw data are placed in the OUT_X, OUT_Y and OUT_Z registers, and both single

read and read_burst (X, Y & Z with auto-incremental address) operations can be used. In

read_burst mode, when data included in OUT_Z_H is read, the system again starts to read

information from addr OUT_X_L.

The reading from FIFO may be executed either in synchronous or asynchronous mode. For

correct data acquisition, the following points need to be followed:

If reading is synchronous, all data should be acquired within one ODR cycle

If reading is asynchronous, an appropriate FIFO access sequence must be applied:

A single dummy read @ 28h (increment bit = 0) to update data out

A burst read of 6 bytes from 2Ah (Y low) up to 29h:

–

Y(2A-2Bh)

–

Z(2C - 2Dh)

–

X(28-29h)

Figure 10 illustrates the correct sequence with a flow diagram:

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